The present invention relates to an expression cassette and plasmids containing this expression cassette. The DNA sequence of the expression cassette contains a transcriptional regulatory starter region, that ensures a specific gene expression in the guard cell of the leaves of plants, and no expression in mesophyllic cells or epidermal cells of the leaves. The invention further relates to a process for the preparation of transgenic plant cells, which contain sequences of the expression cassette as well as the use of the plasmids containing expression cassette for the preparation of transgenic plants.
Because of the continual growth in world population, there is a continual growing demand for nutrient and raw materials and, because of the foreseeable long-term limitation of agricultural land, it is the continuing task of biotechnological research to strive for the production of high yielding ecologically acceptable crops. To achieve this, the metabolism of plants has to be modified. This can be achieved, among other ways, by altering the DNA in the cell nucleus. The process for genetic modification of dicotyledenous and monocotyledenous is already known, (see for example Fraley, R. T. (1989) Science 244: 1293-1299; and Potrykus (1991) Ann Rev Plant Mol Biol Plant Physiol 42: 205-225).